Thread by @sapessi

Interrupting the regular tech programming for another #adventure #motorcycle 🧵 thread.

I see people running to spend big 💵 on motorcycle mods and suspension upgrades when their bike feels slightly uncomfortable. A few clicks on the suspension adjustments can change everything

I couldn't find practical guides to suspension setup for dummies such as myself on the net, so I came up with my own.

First a few disclaimers: I'm primarily interested in (and cover) offroad riding; I assume you can set sag/preload for yourself, I won't spend any time on it.

Before we get into the methodology, let's demystify some terminology. For each term, I give its purpose and our desired outcome.

Compression damping
Purpose: Controls how quickly suspensions compress when hitting an obstacle. Increasing the damping makes the suspension feel stiffer.
Outcome: Use as much of the suspension travel as possible to improve traction and a more plush ride without bottoming out.

Some bikes (esp shocks) have separate high- and low-speed compression damping settings. High-speed damping applies to obstacles on the trail such as rocks that cause the suspensions to compress quickly. Low-speed compression applies to longer undulation on the road.

Rebound damping
Purpose: Controls how quickly suspensions extend following a compression.
Outcome: Make sure the suspension can absorb multiple bumps in succession without bottoming out; push the wheel back against the ground quickly following a compression to maintain traction.

I tried to work on a methodology that can applied quantitatively. The truth is that how the bike "feels" depends on your bike, experience, speed, technique, weight, and oh so many other factors. To find something that "feels" right, we must first create a controlled environment.

Start by picking a trail section that we'll ride over and over to get a feel for the changes. It must meet three requirements: First, you are familiar with it. You should have 80% brain capacity spare to "feel" how the bike behaves, not worry about how big that rock coming up is.

Second, the trail should be "representative" of your average ride. You don't want to set up your suspension for hard enduro when 99% of your riding is packed gravel on wide forest service roads. Third, you should be able to ride this at your average speed. Same reason as for #2.

Have you picked a trail and you are ready to go? Good. We'll start with compression damping. As per the definition, our objectives is to get a plush ride by using as much of the suspension stroke as possible.

To measure this, tie a ziptie to your forks and shock just under the seal. The ziptie should be tight enough not to move by itself, yet not so tight that it will destroy your seals. The point is that when the suspension compresses it pushes the ziptie down the inner tube.

Ride your section of trail at your average speed. At the end, stop, dismount, and check how far down the zipties reached. You want to leave yourself ~10% of the stroke for emergency situations but otherwise they should have been pushed pretty far (90%).

If they have not, follow your bike's manual to reduce the compression damping. In some cases, it's helpful to try extremes (within reason) so that you can truly "feel" the difference and perform something similar to a binary search of the right settings.

If you do have separate fast- and slow-damping settings I would recommend finding two trails: Rocks for fast damping and whoops for slow damping. Theory on testing and adjusting remains the same. The bike should feel planted and small obstacles should be almost entirely absorbed.

On to rebound damping. As a reminder, we just don't want our bike to act like a pogo stick, we just want the wheel to be pushed back against the ground as quickly as possible. I used two separate tests.

The first is similar to the compression damping. Ride a section of the trail that has multiple obstacles in quick succession to stress the suspension and cause cumulative compressions. At the end, check the zipties. We want to end up with our usual 10% safety buffer.

This means the suspension rebounded quickly enough in between obstacles and the cumulative compressions did not cause our suspensions to bottom out. If it did bottom out or go to far in the stroke, follow your manual to decrease the rebound damping to allow faster rebounds.

Next test is a little less precise but helpful nonetheless. I placed a GoPro at ground level and set it to record at slowmo speed (240fps) at a section of the trail with lots of smaller rocks and obstacles.

Afterwards, I checked the footage to make sure that my wheels were pushed against the ground quickly after hitting an obstacles and they were causing the entire bike to jump up.

You can feel good rebound damping settings by having better traction on loose and rocky trails. Your wheels spend more time against the ground and you don't spin as much.

Whew, that was way longer than I expected. Hope it helps someone else.

Oh. One final note. If you are struggling to balance compressions and rebound because one click shifts it too much one way or the other, it's time to look at tire pressure.